Parorchis ralli, Dronen & Blend, 2008

Dronen, Norman O. & Blend, Charles K., 2008, Observations on the Parorchis acanthus complex (Philophthalmidae: Parorchiinae) with the description of three new species of Parorchis Nicoll, 1907 and the replacement of the preoccupied junior homonym Paratrema Dronen & Badley, 1979 with Stenomesotrema nomen novum, Zootaxa 1843 (1), pp. 1-23 : 13-16

Parorchis ralli n. sp.

( Figs. 13–16)

Type host: Clapper rail, Rallus longirostris Boddaert , Gruiformes , Rallidae .

Type locality: Vicinity of Galveston , Galveston County, Texas, U.S.A. (29 º 18' N latitude, 94 º 48' W longitude) .

Site of infection: Rectum.

Deposited specimens: USNPC holotype 100618 .

Prevalence: 5 of 8 laughing gulls, 63%.

Intensity: 1–4 per infected bird.

Etymology: The species is named for the genus of the host bird, Rallus Linnaeus.

Description: Based on 6 adult specimens. Body distinctly pyriform, heavily spinose along periphery and on ventral surface on anterior 50% of body, moderately large, 5,820 (5,680 –5,960) long by 2,550 (2,175 – 2,925) wide; body spines generally thorn-like on periphery, blunter towards midline of body, scale-like, 21

(18–24) long by 15 (11–18) wide; forebody 1,670 (1,500 –1,835, approximately 29% of body length) long by 1,090 (1,050 –1,130) wide, anterior end surrounded by well-developed, shoulder-like head collar 825 (750– 900) wide, bearing a single row of 62 (60–63) thumbnail-shaped, scale-like spines, distinctly notched at both anterior corners; dorsal collar spines, 19 (16–23) long by 11 (8–13) wide; ventral corner spines, 24 (23–25) long by 12 (11–13) wide, typically 12–14 per side. Mouth subterminal; oral sucker wider than long, 385 (365– 400) long by 450 (420–475) wide; prepharynx short to absent, 6 (2–15) long; pharynx longer than wide, 190 (180–205) long by 120 (110–130) wide, ratio of width of pharynx to width of oral sucker 1:3.8 (1:3.7–3.8); esophagus long, 875 (770–980) long with 12-15 short, pouch-like diverticuli; ceca long, terminating near posterior extremity. Acetabulum large, 1,019 (960–1,075) long by 1,120 (990–1,250) wide, sucker ratio 1:2.5 (1:2.4–1:2.6). Testes side by side, deeply lobed, near posterior extremity; left testis 570 (460–630) long by 570 (510–630) wide; right testis 520 (460–580) long by 555 (430–680) wide; intertesticular space 25 (20–30); posttesticular space 825 (700–950) long. Genital pore immediately anterior to acetabulum near midline of body; cirrus sac lateral width 265 (187–343), enclosing cirrus and prostate gland cells, lacking internal seminal vesicle; external seminal vesicle 1,438 (1,400 –1,475) long by 125 (110–135) wide, enclosed in sac-like membrane, overreaching the acetabulum a short distance posteriorly, posterior third tubular and coiled. Ovary oval to round, situated immediately anterior to intertesticular space, about 130 (100–160) anterior to level of testes, near midline of body, 220 (190–250) long by 224 (187–260) wide; ratio of width of ovary to average width of testes 1:2.5 (1:2.5–1:2.5). Morphologically distinct seminal receptacle absent. Laurer’s canal not observed. Vitelline follicles distributed in lateral fields from level of posterior margin of acetabulum posteriorly to level of posterior margin of ovary. Uterus filling hindbody from midlevel of testes to acetabulum, extracecal uterine loops present, proximal end unmodified, filled with spermatozoa; metraterm well developed 210 (179–240) long by 76 (52–90) wide. Eggs variable in size, eggs prior to miracidial eyespot development 59 (57–60) long by 33 (28–36); eggs with fully developed miracidia 77 (70–86) by 42 (33–47); extended miracidia free in uterus 88 (80–94) by 44 (39–49). Excretory vesicle slender, Y-shaped, branching at level of mid-posttesticular space; excretory arms with moderate branching, anterior extent of arms not observed. Excretory pore slightly subterminal on dorsal surface.

Remarks: Parorchis ralli n. sp. is unlike P. acanthus , as originally described by Nicoll (1906) (subtype 1 of the Parorchis body type), by having a larger body size (5,820 long compared to 3,910), a longer esophagus with prominent diverticuli (875 compared to short to “absent” without diverticuli), a somewhat smaller oral sucker (450 wide compared to 500), a smaller pharynx (190 long compared to 240), a slightly larger acetabulum (1,120 wide compared to 1,080), an external seminal vesicle where the posterior third is coiled rather than being straight and club-shaped, and the testes of P. ralli n. sp. are deeply lobed compared to being “circular” and smooth to slightly irregular.

The new species is similar to the specimens used in the redescription of P. acanthus by Nicoll (1907b) (subtype 2 of the Parorchis body type) by having a long esophagus that has diverticuli and testes that are deeply lobed. It differs from these specimens of P. acanthus by having a larger body size (5,680 –5,960 compared to 3,000 –5,000), a somewhat smaller oral sucker (450 wide compared to 500; although Nicoll [1907b] reported the width of the oral sucker to be 500, it appears to be only about 370 wide, as calculated from Figure 1 of Nicoll [1907b], in which case, the oral sucker would be larger in the new species), a shorter prepharynx (0–6 long compared to 110), and a smaller pharynx (190 long by 120 wide compared to 240 by 170; although Nicoll [1907b] reported the width of the pharynx to be 170, it appears to be about 280, as calculated from Figure 1 of Nicoll [1907b]). The new species also has a larger ratio of width of pharynx to width of oral sucker (1:3.8 compared to 1:2.9 using 170 for the width of the pharynx and 500 as the width of the oral sucker as was reported by Nicoll [1907b], or 1:1.3 using approximately 280 wide and 370 wide, respectively, as calculated from Figure 1 of Nicoll [1907b]), a slightly larger acetabulum (1,120 wide compared to 1,080; although Nicoll [1907b] reported the width of the acetabulum to be 1,080, it appears to be about 840, as calculated from Figure 1 of Nicoll [1907b]), a somewhat larger sucker ratio (1:2.5 compared to approximately 1:2.2 using 500 as the width of the oral sucker and 1,080 as the width of the acetabulum, as reported by Nicoll [1907b], or 1:2.3 using approximately 370 wide and 840 wide, respectively, as calculated from Figure 1 of Nicoll [1907b]), and the posterior third of the external seminal vesicle is coiled rather than being straight and clubshaped.

The new species can be distinguished from all species of Parorchis , including Parorchis catoptrophori n. sp. and P. longivesiculus n. sp. described herein, by having the posterior third of the external vesicle coiled rather than being straight and club-shaped, and the new species has a larger ratio of the width of the pharynx to the width of the oral sucker (1:3.8 compared to 1:1.5–1:2.9). The new species has collar spines that are notched on each side along the anterior margin. No other specimens in this study show this characteristic and it may be that this characteristic can be used to distinguish it from other species; however, this feature is difficult to see and could be easily overlooked, and may be present in other species. The new species further differs from P. chauhani by having a larger body size (5,820 long by 2,550 wide compared to 2,795 by 1,298), larger suckers (oral sucker 450 wide compared to 240; acetabulum 1,120 wide compared to 580), larger testes (average testes width 563 compared to 159), and by having slightly larger eggs (70–86 long by 33–47 wide compared to 61–72 by 26–32). Parorchis ralli n. sp. can be distinguished from P. parvicollis and P. snipis because of its larger body size (5,820 long compared to 2,530 and 2,580, respectively), and its larger suckers (oral sucker 450 wide compared to 286 and 270; acetabulum 1,120 wide compared to 584 and 550). The new species differs further from P. schachtachtinskoi by having an overall larger body size (5,820 long by 2,550 wide compared to 4,448 by 1,408), a smaller pharynx (190 long by 120 wide compared to 240 by 210), a larger acetabulum (1,120 wide compared to approximately 1,080), a longer forebody (1,670 long compared to 1,408), and a longer external seminal vesicle (1,438 long compared to 950, as calculated from Figure 1 of Dadasheva & Filimonova [1978]). The new species differs further from P. proctobium by having a smaller body size (5,680 –5,960 long by 2,175 –2,925 wide compared to 5,000 –7,000 by 3,000 –4,000 [measurements from Shtrom 1927]), a smaller oral sucker (450 wide compared to 530 [measurement from Shtrom 1927]), a smaller pharynx (120 wide compared to 190), smaller gonads (ovary 224 wide compared to 400; average width of testes 563 compared to 870), and by having smaller eggs (70–86 long compared to 134–142). Parorchis ralli n. sp. further differs from P. avitus by having a smaller pharynx (120 wide compared to 188), smaller gonads (ovary 224 wide compared to 245; average width of testes 563 wide, compared to 585, as calculated from Figure 3 of Linton [1914]), and a longer external seminal vesicle (1,438 long compared to 1,145, as calculated from Figure 3 of Linton, [1914]). Parorchis magnus n. comb. is larger (7,500 –7,800 compared to 5,820 [5,680 –5,960]), it has a larger pharynx (260–274 wide compared to 110–130), and smaller testes (average testes width 178 compared to approximately 563).